The present invention relates to antimicrobial acrylic fibers which can be used as clothes, fancy goods, interior decorations and materials without exerting a bad influence on the human body and environment, and a process for preparing the same.
Recently, antimicrobial fibers have widely been used as clothes and fiber products for infant and old people for the purpose of inhibiting the growth of various bacteria, thereby to prevent the occurrence of unpleasant odor. Now, the antimicrobial fibers are widely distributed in a market as a product for general consumers in response to consumers"" strong requirements for health and comfort.
In these antimicrobial fibers, various antimicrobial agents are used and a process of incorporating the antimicrobial agents in the fiber products varies with purposes. As the antimicrobial agent, for example, there have been known those disclosed in a technique using an inorganic metal substance including a silver-zeolite system (Japanese Patent Kokai Publication No. 5-272008, etc.), a process of adding fine powders of copper compound or metals such as copper and zinc (Japanese Patent Kokai Publication No. 115440/80, etc.), a process using a derivative of a quaternary ammonium salt (Japanese Patent Kokai Publication No. 130371/84), a process using a halodiallyl urea compound such as trichlorocarbanilide (Japanese Patent Kokai Publication No. 259169/90), and processes using other compounds such as thiabendazole type compound (Japanese Patent Kokai Publication No. 616/86), phenol type compound (Japanese Patent Kokai Publication No. 252713/85, etc.) and fatty acid ester compound (Japanese Patent Kokai Publication No. 6173/88, etc).
However, there is a problem that, when fibers obtained by incorporating silver or copper compounds are subjected to a bleaching treatment, the antimicrobial activity is lost by degradation of silver and copper compounds. In case of some fiber obtained by incorporating an organic compound, there is also a problem that the antimicrobial agent is eliminated by posttreatments, such as dyeing and softening, and washing, thereby to lose the antimicrobial activity and the possible formation of injurious material can not be denied under conditions of usual service environments including posttreatments and discarding.
Under these circumstances, an agent for imparting functional characteristics of a natural antimicrobial agent has attracted special interest recently. For example, it has been considered that hinokitiol extracted from Aomori hiba and Taiwan hinoki has functions such as antimicrobial, antifungal and mothproofing properties, whereas, chitosan as a deacetylated substance of natural polysaccharides chitin obtained from Crustacea has various functions such as antimicrobial/deodorizing, effect for inhibiting the growth of MRSA, high moistureproofness, and prevention and improvement of atopic dermatitis. There has been known a case that a pleasant feeling can be obtained when these agents are used in clothes by incorporating in fibers.
As a process of adhering chitosan to acrylic fibers, for example, a process using an adhesive, a process of incorporating fine powders of chitosan into a spinning stock solution and a process of treating fibers with an acidic solution of chitosan have been known. However, when chitosan is adhered to the fibers using an adhesive, the adhesive causes cohesive curing by a cohesive action of chitosan. Furthermore, when a trial of exerting a peculiar function of chitosan is made, the washing resistance is inferior because the amount of the adhesive is limited. Even if chitosan is ground into fine powders and the powders are uniformly dispersed in an acrylonitrile polymer solution, and then the solution is spun by a publicly known method, it is difficult to spin with good productivity because clogging of a spinning aperture of a spinning nozzle occurs.
Furthermore, the antimicrobial activity of the chitosan-containing acrylic fibers obtained by a process of immersing acrylic fibers in an acidic solution of chitosan and neutralizing the acrylic fibers in an alkali bath, thereby to deposit chitosan on the surface of the fibers is lost by posttreatments such as dyeing and softening, and washing.
Under these circumstances, generally judging, exertion of the antimicrobial/deodorizing function using chitosan, retention of the effect, and retention of fiber performances peculiar to the fibers, such as feeling are not satisfactory at present.